1. Field of the Invention
The invention relates to a print system in which a computer and a printer are connected and data transfer apparatus and method for transferring data from a computer to a printer connected thereto.
2. Related Background Art
Hitherto, a print system for printing by a printer on the basis of a raster image from a host computer has been known. Image data such as characters, figure, or the like formed by application software on the host computer is once developed in a virtual page memory on the host computer. The image data is divided into bands and developed, as an image, in a band memory every image data of each of the obtained bands in accordance with a data output request from an OS (operating system) or application. The data developed in the band memory is sent to an image output apparatus in accordance with a control from the OS or application indicative of the completion of the drawing of the whole band area.
A flow of the data in a band process is as shown in, for example, FIG. 8. For example, the development into the band memory in a printer driver based on a draw command from the application and the output to the printer from the band memory are separately and alternately performed.
In such a print system, since the image developing process and the outputting process to the image output apparatus are alternately performed in the host computer, a large amount of data is sent to the image output apparatus, so that the image output apparatus is in a busy status such as a reception buffer full or the like in many cases.
In such a print system, when the image output apparatus once enters the busy status, the host computer enters a standby mode until the busy status of the image output apparatus is cancelled. On the other hand, when the image development is started by the host computer, the image output apparatus waits for the end of the image development. Therefore, there is a limitation in reduction of a job processing time and a job process cannot be performed at a high speed any more.
When the reception buffer of the image output apparatus once enters the busy status, the control is not returned to the system of the host computer until the busy status of the image output apparatus is cancelled and the output of all data to the image output apparatus is finished.
Particularly, since the image developing process and the process for outputting the data to the image output apparatus are collectively alternately performed by the control from the OS or application, a large amount of data is sent to the image output apparatus at an output timing, so that the apparatus enters the busy status and the host computer often waits for the cancellation of the busy status of the image output apparatus. During the image developing process, the image output apparatus is likely to wait for the process of the host computer. Therefore, the image development of each draw data is processed at a very high speed, the number of requesting times is also very large, and an overhead occurs in the output and the developing process every developing process.